In liquid sensors for detecting the presence of liquid, such as a liquid level sensor and a liquid leakage sensor, conventionally, various detection methods have been used. In the contact type, the electrostatic capacitance method, the electro resistance method, and the like are used, and, in the non-contact type, the ultrasonic method, the optical method, and the like are employed. In each of such liquid sensors, the electrical difference between a state where liquid exists in a detection point, and that where liquid does not exist is obtained, and the presence of liquid is electrically detected. Such liquid sensors function as an electrical load which consumes power supplied from a power supply.
As an air improving device having such a liquid sensor, for example, Patent Literature 1 discloses a battery or AC power-driven evaporator in which aromatic liquid stored in a vessel is evaporated and discharged into a room so that the user can comfortably stay in the room. In the evaporator, when the aromatic liquid in the vessel is consumed, the aromatic effect is lost. Since the vessel is housed in a casing, it cannot be seen from the outside. Therefore, the evaporator includes a residual liquid sensor, and a situation where a small amount of the aromatic liquid remains in the vessel is informed to the user by using a lamp configured by a light-emitting diode.
The evaporator is configured so that a narrow tube is inserted into the vessel, the narrow tube is impregnated with the aromatic liquid to suck up the liquid by means of the capillary action, the sucked aromatic liquid is evaporated by a heater, and the evaporated liquid is discharged by the air current caused by a fan into the room. An aroma substance (simple aroma device) is known which is configured by aromatic liquid, a vessel containing the aromatic liquid, and a sucking wick that is inserted into the vessel, and that is impregnated with the aromatic liquid to suck up the liquid by means of the capillary action, and which causes the aromatic liquid sucked to an upper end portion of the sucking wick to vaporize. In such an aroma substance which does not require a power supply, a residual liquid sensor and lamp which are electrical loads are not used, and, in order to enable the user to visually check the remaining amount of the aromatic liquid in the vessel, each of the vessel, a printing film covering the vessel, and the like are made of a translucent material at the cost of degrees of freedom in design of the exterior, and the aromatic liquid is colored so that its visibility is improved.